1. Field of the Invention
The present invention relates to a rear projection apparatus which facilitates replacement of a lamp.
2. Description of the Related Art
Projectors modulate illumination light by an image display panel with respect to each pixel, and display images on a large-screen by magnifying and projecting image light which carries image information. There are a front type projector, which projects the images from the front of a screen, and a rear type projector, which projects the images from behind the screen.
In recent years, a rear projection apparatus, which utilizes a rear projector as a large-screen television, receives attention. The rear projection apparatus has a translucent screen incorporated in a housing, and accommodates a plane mirror, which is installed in the housing, and a projector unit for projecting the image light to the plane mirror. The interior of the housing of the rear projection apparatus is hollow, so that it is possible, for instance, to use the same projector unit for the rear projection apparatus with different screen size by adjusting a projection distance by changing the arrangement of the projector unit.
Since the projector unit of the rear projection apparatus is continuously used for a long time, a life of a lamp, which illuminates the image display panel, expires in a relatively short term. Therefore, it is preferable that a user can replace the lamp without asking a lamp replacement service. For that reason, it is desirable, for instance, to constitute the lamp as a unit, which enables the user to replace the lamp only by taking out and inserting the lamp to the housing like a cartridge. There is a conventional rear projection apparatus provided with two lamps, so when a life of one lamp is expired, the other lamp is used as a spare lamp to avoid replacement of the expired lamp at a high temperature, and it also prevents interruption of image projection while replacing the lamp (Japanese Patent Laid-Open Publication No. 2000-112026 and No. 2001-264878).
As for the rear projection apparatus of the present invention, the same projector unit can be used for the rear projection apparatuses with the different screen size. However, there are cases where it becomes necessary to change a direction of the image light projection of the projector unit according to inclination of the plane mirror or a projection distance. For that reason, in prior art disclosed in the above references, a posture for setting the projector unit must be changed according to the screen size of the rear projection apparatus. A change in the posture of the lamp makes it hard to take out the lamp, so that there arises a problem that the replacement of the lamp becomes difficult.